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(No Model.)

0. E.- SGRIBN ER. TELEPHONE EXCHANGE SYSTEM.

No. 415,573. Patented'Nov. 19, 1889.

NITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE IVESTERN ELECTRIC COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SBECIFICATION forming part of Letters Patent No. 415,573, dated November 19, 1889.

Application filed June 13, 1387. Serial No. 241,119. (N model.)

To aZZ whom it may concern:

Be it known that 1, CHARLES E. SCRIBNER, a citizen of the United States, residing at Chi- .cago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Case 138,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying draw- .ings, forming a part of this specification.

My invention relates to telephone-exchange systems, and more especially to that system in which the signals from the different stations are sent in over a common line to a lis- .tening operator at the central office, who has a telephone in the circuit of that common line.

My invention relates more particularly to the apparatus at the subscribers station; and

.its object is to enable a subscriber to connect his individual telephone into the general circuit to speak to the operator at the central office or to connect his telephone into his own individual line, over which he converses with other subscribers. Ileretofore this has been accomplished by means of a switch which broke into the signal-circuit to loop the subscribers telephone therein. This system of breaking into the circuit is objectionable,

since at each subscribers station contact- .points must be employed, which, if they should fail to operate properly at any one point, would .disorganize the whole system.

Myinvention consists in providing at each 3 5 of the different subscribers stations an induction-coil, one winding of the coil being included in the signaling-circuit and the other coil being included in the circuit of a switch by means of which the telephone may be included in a local circuit with said winding. By this arrangement I avoid the liability of disorganizing the system by trouble at one station, since the only effect of failure of the apparatus to work properly at one station would be to leave open the circuit of one winding of the induction-coil, this winding being the one connected with the switch. The signaling circuit will thus always remain integral. I preferably provide for shunting out the resistance of that winding of the coil which is in the general circuit an extra contact upon the switch, this being sufficient to do the work. This point, should it fail to operate, merely leaves alittle more resistance in the circuit, but does not render it inoperafive.

My invention is illustrated in the accompanying drawings, in which-- Figure 1 represents four stations connected with the central office. Fig. 2 is a detail view upon lineac ncof Fig. 1 of the loop switch or commutator used at each of the stations.

At station 3 of Fig. 1 I have shown the telephone call-box and loop-switch with the circuit-connections in detail. The signalingcircuit a may be a metallic circuit extending from the listening operators telephone 1) through each of the stations 1 2 3 4 and back to the telephone at the central station.' From each of these stations an individual line 0 eX- tends to the central station, where it is @011- nected with its connecting-bolt or springjack.

The subscriber at station 3, wishing a connection, takes down his telephone, as shown, 7 and at once speaks into his transmitter (1, thus communicating with the listening operator at telephone b. The listening operator ascertains whether the line called for is busy in any of the well-known ways, and if he finds that it is free he proceeds to connect theline c of the calling subscriber with the line wanted. Thus, as shown at switch-board e, spring-jack f of line 0 is shown connected with springjack 9 of line 0 bythe flexible cord h, provided with terminal plugs.

At the central office I have shown two sections of a multiple switch-board. The 0011- necting apparatus'I have not shown in detail, since it is well known, and therefore needs no description.

The subscribers loop-switchi may be of any form capable of doing the work. I have for clearness shown a switch having three springfingers 701m attached to a rubber strip. A key- 5 knob is mounted upon the spring, and by means of this knob the spring-fingers are pushed in or drawn out to make the necessary connections. This will be understood by reference to Fig. 2. Contact-points correspond- I00 ing tosaid spring-fingers are provided upon a base.

The spring-fingers are mounted upon the same base and arranged to be moved back and forth to connect with or be separated from the contact-points to make the necessary changes of circuit. The switch being pushed in and the telephone removed from the hook, as shown at station 3, the circuit-connections will permit subscriber 3 to speak to the listen.- ing operator at telephone 1) over the circuitwire a. Thus the circuit may be traced from telephone binding-post 0 to spring-finger 7c, and thence by wire 1) through the winding of the induction-coil, thence by wire (1 to springfinger Z, and thence by wire 0" to the other telephone bindingpost 3. The subscriber thus speaking into the transmitter (1 causes undulatoryvoice-currents to be sent through the local short circuit, which includes a winding of the induction-coil as before traced. The spring-finger m, having been pushed in simultaneously with the springs 7c Z, is moved from its contact-point t, and thus the normal shunt around the induction-coil is opened. Thevoice-current, therefore, sent through the winding of the induction-coil included in the local circuit will induce corresponding currents in the signaling-circuit a, which is connected directly through the other winding of the induction-coil at said station 3. The subscriber, having communicated with the listening operator and obtained the service required, moves the loop-switch back to the position shown in Fig. 2. The shunt is thereupon closed between spring finger m and point t around the signaling-circuit winding ofthe induction-coil. Spring-finger Z is disconnected from its connection with wire q and spring-finger 713 from its connection with wire 19, while a new connection is formed between spring-finger 7e and its normal contact-point n. The local circuit through the subscribers winding of the'induction-coil is thus opened and the circuit of the subscribers individual line 0 may be traced, beginning at ground at station 3, thence to posts, and thence through the telephone in the usual manner to post 0, thence to spring-finger 7c and contact a, and thence over wire 0 to the spring-jack f at the central office. Springjackf being connected with the spring-jack g, the circuit may be further traced from spring-jack f through cord h to spring-jack g, and thence by wire 0 to subscribers station 1, and through his telephone apparatus, in the usual manner, to ground, asbefore described with respect to station 3. Then the subscribers are through talking, one or the other switches back to the signaling-circuit and signals offthat is, tells the listening operator that he may disconnect.

In Fig. 2 I have shown a spring t, which normally holds the switch in position to close the circuit of the shunt between contact tand spring-finger m. When the spring o is used, the sutscriber while talking constantly presses the button in to bring the switch to the position shown at station 3, Fig. 1. On removing his finger from the button the resiliency of spring '0 causes the switch to assume the position shown in Fig. 2.

Having thus described my invention, I claim as new and desire to secure by Letters Patent 1. The combination, in a telephone exchange system, with the signaling-circuit including several stations and a telephone permanently connected in the signaling-circuit at the central office, of individual telephonelines radiating to the different stations and an induction-coil and switching apparatus at each station, whereby any subscriber may connect his telephone into a local circuit including one of the windings of the inductioncoil, the other winding of the induction-coil being included in the signaling-circuit.

2. In a telephone-exchange system, the signaling-circuit extending from the central officeto several subscribers stations, individual telephone-lines extending from the central office to the several subscribers stations, one line to each station, telephone apparatus and switching devices, and an induction-coil having one winding included in the circuit of the signaling-wire, the other winding connected in a local circuit through the subscribers telephone, substantially as described.

3. The combination, at a subscribers station, of an induction-coil with a signal-circuit including one of the windings of said coil and a shunt-circuit around said winding, a local circuit including the subscribers telephone and the other winding of the induction-coil, and switching apparatus connected to open the said shunt-circuit at the same time the said switching apparatus closes the local circuit, whereby the subscribers telephone may be connected with the signalingcircuit or disconnected therefrom, as described.

4. The co1nbination,with an induction-coil, of a signaling-circuit including one winding of the said coil, a shunt-circuit around said windin g, said shu nt-circuit including a switching device, a telephone included in the circuit of the other winding of the inductioncoil, a switching device included in the circuit of said telephone and winding, the two switching devices being connected to operate at the same time, whereby the shunt-circuit is automatically closed when the telephonecircuit is interrupted, and whereby the shuntcircuit is interrupted when the telephone-circuit is closed.

In witness whereof I hereunto subscribe my name this 1st day of June, A. D. 1887.

CHARLES E. SORIBNER. lVitnesses:

GEORGE P. BARTON, C. O. WooDwoRTH.

ICC 

